Method for manufacturing planar transformer with odd turn ratio

ABSTRACT

A method for planar transformer with an odd turn ratio includes: determining a turn ratio and winding parameters of a transformer to be manufactured; if the turn ratio is odd, determining that there is respectively one winding turn on a first middle layer and a second middle layer and two winding turns on a top layer and a bottom layer; determining widths of winding wires on marginal layers as well as widths of winding wires on middle layers; winding and parallelly connecting an inner winding wire on the top layer to an inner winding wire on the bottom layer, and then serially connecting the parallel-connected inner winding wires to an outer winding wire to form a primary winding; and parallelly connecting the winding wire on the first middle layer to the winding wire on the second middle layer to form a secondary winding, so as to obtain the transformer.

TECHNICAL FIELD

The present disclosure relates to the technical field of design ofplanar transformers, in particular to a method for manufacturing aplanar transformer with an odd turn ratio.

BACKGROUND

In recent years, scientific and technological advances bring continuousimprovement of power electronics. Isolation transformers have beenwidely used in the fields of new energy and distributed generation.Furthermore, with continuous improvement of magnetic integration, planartransformers have received more extensive attention on the aspects ofapplication and technical research. The winding of most planartransformers is performed on printed circuit boards (PCBs), andsingle-layer winding or asymmetric multi-layer winding are generallyadopted in a case of odd turn ratio. Such traditional winding modesrequire a large window area of magnetic cores or an increase in layersof the PCBs. As a result, the volume and design cost of the transformersare increased. Besides, asymmetric structures such as 2+1 structureswill be caused by multi-layer structures in most cases. This may affectthe distribution of magnetic fields of the transformers, and reduce theefficiency of the transformers.

When a planar transformer with an odd turn ratio is manufactured,asymmetry of the magnetic fields and low operating efficiency will becaused by the traditional winding modes.

SUMMARY

The present disclosure aims to provide a method for manufacturing aplanar transformer with an odd turn ratio. In this method, inner windingwires are connected in parallel and then are connected in series to anouter winding wire which is not as wide as the inner winding wires, soas to form a primary winding; and in this way, a well-distributedmagnetic field can be generated, so that operating efficiency of theplanar transformer can be improved.

To achieve the above objective, the present disclosure provides thefollowing solutions:

A method for manufacturing a planar transformer with an odd turn ratioincludes:

determining a turn ratio and winding parameters of a transformer to bemanufactured, where the winding parameters include a radius of amagnetic core, a length of a coil layout window, a winding resistance,and a winding thickness, and the transformer to be manufactured has afour-layer PCB including a bottom layer, a first middle layer, a secondmiddle layer, and a top layer which are sequentially arranged frombottom to top;

if the turn ratio is odd, determining that there is respectively onewinding turn on the first middle layer and the second middle layer andtwo winding turns on the top layer and the bottom layer;

determining widths of inner winding wires and outer winding wires onmarginal layers as well as widths of winding wires on middle layersaccording to the winding parameters, where the marginal layers includethe top layer and the bottom layer, and the middle layers include thefirst middle layer and the second middle layer;

winding according to the number of winding turns on the marginal layersand the middle layers, the widths of the inner winding wires and outerwinding wires on the marginal layers, and the widths of the windingwires on the middle layers; parallelly connecting the inner windingwires on the top layer to the inner winding wire on the bottom layer,and then serially connecting the parallel-connected inner winding wiresto an outer winding wire, so as to form a primary winding; andparallelly connecting the winding wire on the first middle layer to thewinding wire on the second middle layer to form a secondary winding, soas to obtain the transformer winding; where the outer winding wire isformed by serially connecting the outer winding wire on the top layer tothe outer winding wire on the bottom layer.

According to specific embodiments, the present disclosure has thefollowing technical effects:

The method for manufacturing a planar transformer with an odd turn ratioincludes: if the turn ratio is odd, determining that there isrespectively one winding turn on the first middle layer and the secondmiddle layer and two winding turns on the top layer and the bottomlayer; winding according to the number of winding turns on the marginallayers and the middle layers as well as the widths of the inner windingwires and outer winding wires on the marginal layers and the widths ofthe winding wires on the middle layers, which are determined accordingto the winding parameters; meanwhile, parallelly connecting the innerwinding wire on the top layer to the inner winding wire on the bottomlayer, and then serially connecting the parallel-connected inner windingwires to the outer winding wire formed by serially connecting the outerwinding wire on the top layer to the outer winding wire on the bottomlayer, so as to form the primary winding; and parallelly connecting thewinding wire on the first middle layer to the winding wire on the secondmiddle layer to form the secondary winding, so as to obtain thetransformer. In this method, the inner winding wires are parallellyconnected to each other and then are serially connected to the outerwinding wire which is not as wide as the inner winding wires, so as toform the primary winding; and in this way, operating efficiency of theplanar transformer can be improved.

BRIEF DESCRIPTION OF DRAWINGS

For the sake of a clearer explanation of the technical solutions of theembodiments of the present disclosure or the prior art, the accompanyingdrawings required by the embodiments will be described briefly below.Clearly, the following accompanying drawings merely illustrate someembodiments of the present disclosure, and other accompanying drawingscan also be obtained by those ordinarily skilled in the art based on thefollowing ones without creative efforts.

FIG. 1 is a flow chart of a method for manufacturing a planartransformer with an odd turn ratio in an embodiment of the presentdisclosure;

FIG. 2 is a structural diagram of a primary winding and a secondarywinding in the embodiment of the present disclosure;

FIG. 3 is a top view of a top layer in the embodiment of the presentdisclosure;

FIG. 4 is a top view of a bottom layer in the embodiment of the presentdisclosure;

FIG. 5 is a top view of a first middle layer in the embodiment of thepresent disclosure;

FIG. 6 is a top view of a second middle layer in the embodiment of thepresent disclosure; and

FIG. 7 is a sectional view of the primary winding and the secondarywinding in the embodiment of the present disclosure.

In the figure, 1. inner winding wire on a top layer, 2. first throughhole, 3. second through hole, 4. inner winding wire on a bottom layer,5. winding wire on a first middle layer, 6. third through hole, 7.fourth through hole, 8. winding wire on a second middle layer, 9. outerwinding wire on the top layer, 10. outer winding wire on the bottomlayer.

DETAILED DESCRIPTION

The technical solutions of the embodiments of the present disclosure areclearly and completely described below with reference to theaccompanying drawings. Apparently, the embodiments in the followingdescriptions are only illustrative ones, and are not all possible onesof the present disclosure. All other embodiments obtained by thoseordinarily skilled in the art based on the embodiments of the presentdisclosure without creative efforts should also fall within theprotection scope of the present disclosure.

The objective of the present disclosure is to provide a method formanufacturing a planar transformer with an odd turn ratio. In thismethod, inner winding wires are parallelly connected to each other andthen are serially connected to an outer winding wire which is not aswide as the inner winding wires, so as to form a primary winding; and inthis way, operating efficiency of the planar transformer can beimproved, and such winding mode can be applied to the technical field ofdesign of planar transformers.

To make the objectives, features, and advantages of the presentdisclosure more obvious and understandable, the following furtherdescribes in detail the present disclosure with reference to theaccompanying drawings and specific implementations.

FIG. 1 shows a flow chart of the method for manufacturing a planartransformer with an odd turn ratio in an embodiment of the presentdisclosure. As shown in FIG. 1, the method for manufacturing a planartransformer with an odd turn ratio includes:

Step 101: determine a turn ratio and winding parameters of a transformerto be manufactured, where the winding parameters include a radius of amagnetic core, a length of a coil layout window, a winding resistance,and a winding thickness, and the transformer to be manufactured has afour-layer PCB including a bottom layer, a first middle layer, a secondmiddle layer, and a top layer which are sequentially arranged frombottom to top; and

Determine a winding mode according to the turn ratio, where atraditional method will be implemented to manufacture the transformer ifthe turn ratio is even, and step 102, step 103, and step 104 will beperformed if the turn ratio is odd;

Step 102: if the turn ratio is odd, determine that there is respectivelyone winding turn on the first middle layer and the second middle layerand two winding turns on the top layer and the bottom layer;

Step 103: determine widths of inner winding wires and outer windingwires on marginal layers as well as widths of winding wires on middlelayers according to the winding parameters, where the marginal layersinclude the top layer and the bottom layer, and the middle layersinclude the first middle layer and the second middle layer; and

Step 104: wind according to the number of winding turns on the marginallayers and the middle layers, the widths of the inner winding wires andouter winding wires on the marginal layers, and the widths of thewinding wires on the middle layers; parallelly connect the inner windingwire on the top layer to the inner winding wire on the bottom layer, andthen serially connect the parallel-connected inner winding wires to anouter winding wire, so as to form a primary winding; and parallellyconnect the winding wire on the first middle layer to the winding wireon the second middle layer to form a secondary winding, so as to obtainthe transformer, where the outer winding wire is formed by seriallyconnecting the outer winding wire on the top layer to the outer windingwire on the bottom layer.

FIG. 2 to FIG. 7 show the bottom layer, first middle layer, secondmiddle layer, top layer, primary winding, and secondary winding of theobtained transformer. Where, the inner winding wire 1 on the top layeris parallelly connected to the inner winding wire 4 on the bottom layervia a first through hole 2 and a second through hole 3, and then theparallel-connected inner winding wires are serially connected to theouter winding wire formed by serially connecting the outer winding wire9 on the top layer to the outer winding wire 10 on the bottom layer, soas to form the primary winding; and the winding wire 5 on the firstmiddle layer is parallelly connected to the winding wire 8 on the secondmiddle layer via a third through hole 6 and a fourth through hole 7 toform the secondary winding. Furthermore, the obtained transformer isformed with the first through hole 2 in the top layer, the secondthrough hole 3 in the bottom layer, the third through hole 6 in thefirst middle layer, and the fourth through hole 7 in the second middlelayer; and i_(pri) and i_(sec) respectively represent currents flowingthrough the primary winding and secondary winding of the transformer.

In an optional embodiment, the step of determining a turn ratio andwinding parameters of a transformer to be manufactured specificallyincludes:

Determine the turn ratio and the winding parameters according to anoperating frequency and voltage transformation level of the transformerto be manufactured.

In an optional embodiment, the step of determining widths of innerwinding wires and outer winding wires on marginal layers as well aswidths of winding wires on middle layers according to the windingparameters specifically includes:

Determine the width of the inner winding wire on the top layer accordingto the winding parameters;

Determine the width of the outer winding wire on the top layer accordingto the radius of the magnetic core, the length of the coil layoutwindow, and the width of the inner winding wire on the top layer;

Determine the width of the inner winding wire on the bottom layeraccording to the width of the inner winding wire on the top layer aswell as the width of the outer winding wire on the bottom layeraccording to the width of the outer winding wire on the top layer; and

Determine the width of the winding wire on the first middle layer andthe width of the winding wire on the second middle layer according tothe radius of the magnetic core and the length of the coil layoutwindow.

In an optional embodiment, the step of determining the width of theinner winding wire on the top layer according to the winding parametersspecifically includes:

Create a formula for calculating equivalent impedance as follows:

R _(total)=4ρπr ₁/[(r ₁ −r ₀ −x ₁)h]+ρπ(r ₀ −x ₁)/(x ₁ h);

Where, R_(total) represents equivalent impedance of the primary winding;ρ represents the winding resistance; r₁ represents the length of thecoil layout window; r₀ represents the radius of the magnetic core; x₁represents the width of the inner winding wire on the top layer; and hrepresents the winding thickness; and as shown in FIG. 3, x₁=r₂−r₀;

Derive the formula for calculating the equivalent impedance to obtain aderivative formula; and

Substitute the winding parameters into the derivative formula, and set aderivative of the equivalent impedance of the primary winding as zero,so as to obtain the width of the inner winding wire on the top layer.The formula for calculating the equivalent impedance is derived throughthe following steps:

Create a formula for calculating impedance of a parallel windingaccording to the radius of the magnetic core, the winding resistance,and the winding thickness as follows:

R ₁=ρπ(r ₀ +x)/(xh).

Where, R₁ represents the impedance of the parallel winding;

Create a formula for calculating impedance of the outer winding wireaccording to the winding parameters as follows:

R ₂=ρ4πr ₁/[(r ₁ −r ₀ −x)h];

Where, R₂ represents the impedance of the outer winding wire; and

Create the formula for calculating the equivalent impedance according tothe formula for calculating the impedance of the parallel winding andthe formula for calculating the impedance of the outer winding wire asfollows:

R _(total) =R ₁ +R ₂=4ρπr ₁/[(r ₁ −r ₀ −x ₁)h]+ρπ(r ₀ +x ₁)/(x ₁ h)

In an optimal embodiment, the width of the outer winding wire on the toplayer is determined according to the radius of the magnetic core, thelength of the coil layout window, and the width of the inner windingwire on the top layer specifically as follows:

y₁ =r ₁ −r ₀ −x ₁;

Where, y₁ represents the width of the outer winding wire on the toplayer.

In an optimal embodiment, the width of the inner winding wire on thebottom layer is determined according to the width of the inner windingwire on the top layer and the width of the outer winding wire on thebottom layer is determined according to the width of the outer windingwire on the top layer as follows:

The inner winding wire on the bottom layer is as wide as the innerwinding wire on the top layer, and the outer winding wire on the bottomlayer is as wide as the outer winding wire on the top layer.

In an optimal embodiment, the width of the winding wire on the firstmiddle layer and the width of the winding wire on the second middlelayer are determined according to the radius of the magnetic core andthe length of the coil layout window as follows:

x ₂ =x ₃ =r ₁ −r ₀;

Where, x₂ represents the width of the winding wire on the first middlelayer.

Each embodiment of the specification is described in a progressivemanner, each embodiment focuses on the difference from otherembodiments, and the same and similar portions of the embodiments mayrefer to each other.

Several specific embodiments are used to expound the principle andimplementations of the present disclosure. The descriptions of theseembodiments are used to assist in understanding the method of thepresent disclosure and its core conception. In addition, thoseordinarily skilled in the art can make various modifications in terms ofspecific embodiments and scope of application based on the conception ofthe present disclosure. In conclusion, the content of this specificationshould not be construed as a limitation to the present disclosure.

What is claimed is:
 1. A method for manufacturing a planar transformerwith an odd turn ratio, comprising: determining a turn ratio and windingparameters of a transformer to be manufactured, wherein the windingparameters comprise a radius of a magnetic core, a length of a coillayout window, a winding resistance, and a winding thickness, and thetransformer to be manufactured has a four-layer printed circuit board(PCB) comprising a bottom layer, a first middle layer, a second middlelayer, and a top layer which are sequentially arranged from bottom totop; if the turn ratio is odd, determining that there is respectivelyone winding turn on the first middle layer and the second middle layerand two winding turns on the top layer and the bottom layer; determiningwidths of inner winding wires and outer winding wires on marginal layersas well as widths of winding wires on middle layers according to thewinding parameters, wherein the marginal layers comprise the top layerand the bottom layer, and the middle layers comprise the first middlelayer and the second middle layer; and winding according to the numberof winding turns on the marginal layers and the middle layers, thewidths of the inner winding wires and outer winding wires on themarginal layers, and the widths of the winding wires on the middlelayers; parallelly connecting the inner winding wire on the top layer tothe inner winding wire on the bottom layer, and then serially connectingthe parallel-connected inner winding wires to an outer winding wire, soas to form a primary winding; and parallelly connecting the winding wireon the first middle layer to the winding wire on the second middle layerto form a secondary winding, so as to obtain the transformer; whereinthe outer winding wire is formed by serially connecting the outerwinding wire on the top layer to the outer winding wire on the bottomlayer.
 2. The method for manufacturing a planar transformer with an oddturn ratio according to claim 1, wherein the step of determining a turnratio and winding parameters of a transformer to be manufacturedspecifically comprises: determining the turn ratio and the windingparameters according to an operating frequency and voltagetransformation level of the transformer to be manufactured.
 3. Themethod for manufacturing a planar transformer with an odd turn ratioaccording to claim 1, wherein the step of determining widths of innerwinding wires and outer winding wires on marginal layers as well aswidths of winding wires on middle layers according to the windingparameters specifically comprises: determining the width of the innerwinding wire on the top layer according to the winding parameters;determining the width of the outer winding wire on the top layeraccording to the radius of the magnetic core, the length of the coillayout window, and the width of the inner winding wire on the top layer;determining the width of the inner winding wire on the bottom layeraccording to the width of the inner winding wire on the top layer aswell as the width of the outer winding wire on the bottom layeraccording to the width of the outer winding wire on the top layer; anddetermining the width of the winding wire on the first middle layer andthe width of the winding wire on the second middle layer according tothe radius of the magnetic core and the length of the coil layoutwindow.
 4. The method for manufacturing a planar transformer with an oddturn ratio according to claim 3, wherein the step of determining thewidth of the inner winding wire on the top layer according to thewinding parameters specifically comprises: creating a formula forcalculating equivalent impedance as follows:R _(total)=4ρπr ₁/[(r ₁ −r ₀ −x ₁)h]+ρπ(r ₀ −x ₁)/(x ₁ h); wherein,R_(total) represents equivalent impedance of the primary winding; ρrepresents the winding resistance; r₁ represents the length of the coillayout window; r₀ represents the radius of the magnetic core; x₁represents the width of the inner winding wire on the top layer; and hrepresents the winding thickness; deriving the formula for calculatingthe equivalent impedance to obtain a derivative formula; andsubstituting the winding parameters into the derivative formula, andsetting a derivative of the equivalent impedance of the primary windingas zero, so as to obtain the width of the inner winding wire on the toplayer.
 5. The method for manufacturing a planar transformer with an oddturn ratio according to claim 3, wherein the width of the outer windingwire on the top layer is determined according to the radius of themagnetic core, the length of the coil layout window, and the width ofthe inner winding wire on the top layer specifically as follows:y ₁ =r ₁ −r ₀ −x ₁; wherein, y₁ represents the width of the outerwinding wire on the top layer; r₁ represents the length of the coillayout window; r₀ represents the radius of the magnetic core; and x₁represents the width of the inner winding wire on the top layer.
 6. Themethod for manufacturing a planar transformer with an odd turn ratioaccording to claim 3, wherein the width of the inner winding wire on thebottom layer is determined according to the width of the inner windingwire on the top layer and the width of the outer winding wire on thebottom layer is determined according to the width of the outer windingwire on the top layer as follows: the inner winding wire on the bottomlayer is as wide as the inner winding wire on the top layer, and theouter winding wire on the bottom layer is as wide as the outer windingwire on the top layer.
 7. The method for manufacturing a planartransformer with an odd turn ratio according to claim 3, wherein thewidth of the winding wire on the first middle layer and the width of thewinding wire on the second middle layer are determined according to theradius of the magnetic core and the length of the coil layout window asfollows:x ₂ =x ₃ =r ₁ −r ₀; wherein, x₂ represents the width of the winding wireon the first middle layer; x₃ represents the width of the winding wireon the second middle layer; r₁ represents the length of the coil layoutwindow; and r₀ represents the radius of the magnetic core.